A possible meteor surprise

Posted by Rich Talcott
on Friday, May 04, 2007

It's the first week of May, and that can mean only one thing to naked-eye stargazers: the peak of the Eta Aquarid meteor shower. Normally, that's a pretty big deal. After all, the Eta Aquarids' peak rate ranks fourth among annual meteor showers, behind only December's Geminids, January's Quadrantids, and August's Perseids. Although the shower favors Southern Hemisphere observers, northerners with a penchant for meteor observing rarely pass it up.

Most of us were expecting a less-than-stellar show this year. The shower normally would peak before dawn on May 5. With Full Moon occurring just 3 days earlier, however, the early morning hours of the 5th will be awash in bright moonlight. That will drown out fainter meteors and leave just the brighter ones.

But the show could be much better than expected. Just last week, Mikiya Sato and Jun-Ichi Watanabe of the National Astronomical Observatory of Japan announced the possibility of increased Eta Aquarid activity this year. Inspired by the unexpected outburst last October of the Orionids — the year's other meteor shower derived from Comet 1P/Halley — the two astronomers looked more carefully at dust trails ejected by Halley. They found that Earth will pass through a trail expelled by Halley during its trip through the inner solar system in the 9th century B.C.

If the Eta Aquarid rates jump as much as they did for the Orionids, we could be looking at a zenithal hourly rate (ZHR) of between 100 and 200 meteors. The numbers for northern observers will fall well below the ZHR because the radiant lies well below the zenith and the Moon will still be bright, but the prospects for a good show just grew more favorable.

The outburst's predicted peak is about 14h30m Universal Time on the 6th, which puts it at 10:30 A.M. EDT, 7:30 A.M. PDT, and 4:30 A.M. in Hawaii. But this dust stream is old and complex, so any outburst could last for several hours. I don't know about you, but I'll be out there Sunday morning, seeing if Comet Halley puts on another good show.

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